1. Field of the Invention
The present invention generally relates to a method of fabricating a color filter. More particularly, the present invention relates to a method of fabricating a color filter on a thin film transistor (TFT) array.
2. Description of Related Art
As multi-media technology advances, a variety of semiconductor devices or displays have been rapidly developed. Displays, for example, TFT liquid crystal displays, because of its advantages of high resolution, high space-effectiveness, low power consumption and non-radiation, have become the main trend in this industry.
A TFT liquid crystal display comprises a TFT array substrate, a color filter substrate, and a liquid crystal layer. According to one conventional method, the TFT array substrate and the color filter substrate are manufactured separately, and then a TFT liquid crystal display panel with the liquid crystal layer formed there-between. According to another conventional method, first, a color filter is directly formed on a TFT array substrate for reducing the problems in reduction of aperture ratio and misalignment between the TFT array substrate and the color filter substrate.
FIG. 1A to 1F illustrate a process of fabricating a color filter on a TFT array substrate. First, a substrate 100 having a TFT array 110 thereon is provided, wherein the TFT array 110 comprises a plurality of gates 112, a gate-insulating layer 114, a plurality of semi-conductive layer 116 and a plurality of sources/drains 118a/118b. 
Next, referring to FIG. 1B, a passivation layer 190 is formed over the TFT array 110, and a plurality of openings 170a is formed in the passivation layer 190 to expose the drains 118b. 
Next, referring to FIG. 1C, red filter patterns 150a are formed on the passivation 190. According to an embodiment of the present invention, a red photoresist layer is formed over the passivation layer 190 by spin coating, and subsequently, the red photoresist layer is then exposed and then etched in a conventional photolithography process, and finally baked to form a red filter pattern 150a and openings 170b exposing the openings 170a and thereby exposing the drains 118b. 
Next, referring to FIG. 1D, similarly, the above process may be repeated to form green filtering pattern 150b and blue filter pattern 150c. Furthermore, a black matrix 120 may be formed between the color filters patterns 150a, 150b, and 150c. 
Next, as shown in FIG. 1E, an overcoat layer 160 is formed over the black matrix 120 and the color filtering patterns 150a, 150b, and 150c. And a plurality of contact holes 140 is formed in the overcoat layer 160 to expose the drains 118b. 
Next, as shown in FIG. 1F, a plurality of pixel electrodes 180 is formed over the overcoat layer 160 and electrically connected to the drains 118b of the TFT array 110 through the contact holes 140 respectively.
As described in the above conventional method, red, green, and blue filter patterns are formed separately by coating, photolithography process including exposure and etching, and baking. Therefore, the conventional process not only requires many additional process steps but is also a complicated process in which the risk of reduction in the yields is high. Furthermore, the masking step used for defining the color filter patterns would substantially increase the manufacturing cost. In addition, the difficulty in coating the color photoresist could more obvious and amplified as the size of the TFT substrate is enlarged.